1. Field of the Invention
This invention relates to a lens fitted film unit.
2. Description of Related Art
Film cartridges or cartridges used in what is called an advanced photo system (APS) have a built-in spool which is rotated to advance and forward a film strip out of the cartridge. Such a film cartridge is known from, for instance, Japanese Unexamined Patent Publication No. 6-301157. The film cartridge can be put in and taken out of a camera with the entire length of film strip rolled in the cartridge.
One of this APS type film cartridges (which is hereafter referred to as a film cartridge for simplicity) is shown by way of example in FIG. 4. Generally, the film cartridge comprises a cartridge shell 23 and a cartridge spool 24 rotatable inside the cartridge shell 23 in opposite directions to unwind a filmstrip 22 off the cartridge spool 24 and to wind the filmstrip 22 onto the spool 24. The film cartridge further comprises a light block door 27 rotated closed to prevent ambient light from entering the cartridge shell 23 through a film egress/ingress slot 26 and rotated open to permit the filmstrip 22 to move into and out of the cartridge shell through the film egress/ingress slot 26. A door drive mechanism built-in a camera engages an end portion of the light block door 27 exposed to the cartridge exterior for rotating the light block door between closed and open positions when the film cartridge is taken out of and put in the camera, respectively. The cartridge shell 23 is shaped mostly cylindrical to match a roll of the filmstrip 22 and is partially flat.
When using the film cartridge with a conventional still camera, it is recommended to position the cartridge in the camera with the flat portion 23a of the cartridge shell 23 inclined backward at an angle of approximately 4.degree. with respect to an imaginary plane (shown by dotted broken line A in FIG. 6A) which is defined by an exposure aperture perpendicular to an optical axis of the camera, as shown by chained line B in FIG. 6A. The film cartridge inclined backward at an angle of approximately 4.degree. with respect to the plane perpendicular to the camera optical axis takes substantially the best position for permitting the filmstrip 22 to move out of the cartridge shell 23 without being impeded by the light block door 27 and/or edges of the film egress/ingress slot 26. Owing to this cartridge position, the filmstrip 22 is prevented from receiving increased frictional resistance from the light block door 27 and edges of the film egress/ingress slot 26 and/or catching scratches during film movement into and out of the cartridge interior.
In the case where the APS type film cartridge is employed in lens-fitted film units on which a strong demand for miniaturization is made, the best position of the film cartridge is, however, one which causes an increase in thickness of a light-tight film unit case of such a lens fitted film unit. In particular, because the lens-fitted film unit has an exposure aperture defined by film tracks bending backward as shown in FIG. 6B, the filmstrip 22 (shown by chained line C in FIG. 6B) enters the cartridge interior at an angle of approximately 15.degree. with respect to the plane (shown by chained line A in FIG. 6B) perpendicular to an optical axis of the film unit at the film egress/ingress slot 26. Consequently, when positioning the film cartridge in substantially the best position, namely at an angle of 4.degree. with respect to the plane defined by the exposure aperture, the film cartridge must be placed with an inclination of approximately 19.degree. with respect to the plane perpendicular to the optical axis of the film unit, and hence the flat portion 23a shifted backward. In this way, the light-tight film unit case containing the film cartridge placed in the best position is made thicker, decreasing portability which is one of distinctive features of the lens fitted film unit.
As is well known, at the manufacturer, the light-tight film unit case is loaded with a film cartridge with substantially the entire length of unexposed filmstrip prewound simply into a roll in a film roll chamber located on the opposite side of the film cartridge with respect to the exposure aperture. The exposed frame is rewound into the film cartridge after every exposure. Consequently, the photographer is never required to wind the film strip out of the film cartridge. Owing to the necessity of film movement in one direction only, the filmstrip is not scratched even when it makes a strong contact with the light block door and/or edges of the film egress/ingress slots and thus an increase in frictional resistance is not a serious problem to be settled in the lens fitted film unit.